Technical Field
The present invention relates to brass not containing lead, that is, the so-called lead-free brass. More particularly, the present invention relates to brass for casting possessing improved machinability, castability, mechanical properties and other properties, which, by virtue of freedom from lead, can be advantageously used, for example, for water faucet metal fittings.
Background Art
Water faucet metal fittings are in general made of brass or bronze. From the viewpoint of improving the machinability of the material, lead (Pb) is added in an amount of about 2 to 3% by weight for brass and in an amount of about 4 to 6% by weight for bronze. In recent years, however, the influence of Pb on the human body and environments has become a concern, and regulations related to Pb have been actively established in various countries. For example, in California, U.S.A., a regulation of the content of Pb in a water tap faucet which should be not more than 0.25% by weight from January, 2010, has come into effect. Further, it is said that the leaching amount of Pb would also be regulated to about 5 ppm in the future. Also in countries other than the U.S.A., the movement of regulations about Pb is significant, and the development of materials which can cope with the regulations of Pb content or leaching amount of Pb has been desired in the art.
Japanese Patent H07(1995)-310133 A proposes brass with bismuth (Bi) added thereto instead of Pb because Bi behaves similarly to Pb in brass. Further, Japanese Patent 2005-290475 A discloses that, in a Bi-added system, for example, boron (B) and nickel (Ni) are added from the viewpoint of improving the machinability. Furthermore, Japanese Patent 2001-59123 A discloses that, in a Bi-added system, the addition of iron (Fe) refines crystal grains. In systems disclosed in these prior art techniques, however, there is room for improvement in castability, especially in cracking in casting. Accordingly, there is still a demand for the development of brass free from Pb and having improved castability, machinability, mechanical properties and other properties.